The present application is directed to a system for generating a two-dimensional map of an area, such as a building for example, and in particular to a two-dimensional mapping system that accommodates moving objects, such as doors.
Metrology devices, such as a 3D laser scanner time-of-flight (TOF) coordinate measurement devices for example, may be used to generate three dimensional representations of areas, such as buildings for example. A 3D laser scanner of this type steers a beam of light to a non-cooperative target such as a diffusely scattering surface of an object. A distance meter in the device measures a distance to the object, and angular encoders measure the angles of rotation of two axles in the device. The measured distance and two angles enable a processor in the device to determine the 3D coordinates of the target.
A TOF laser scanner is a scanner in which the distance to a target point is determined based on the speed of light in air between the scanner and a target point. Laser scanners are typically used for scanning closed or open spaces such as interior areas of buildings, industrial installations and tunnels. They may be used, for example, in industrial applications and accident reconstruction applications. A laser scanner optically scans and measures objects in a volume around the scanner through the acquisition of data points representing object surfaces within the volume. Such data points are obtained by transmitting a beam of light onto the objects and collecting the reflected or scattered light to determine the distance, two-angles (i.e., an azimuth and a zenith angle), and optionally a gray-scale value. This raw scan data is collected, stored and sent to a processor or processors to generate a 3D image representing the scanned area or object.
Some systems use the three-dimensional data to generate a two-dimensional map or floor plan of the area being scanned. As the TOF laser scanner is moved, an accurate 2D map of the area (e.g. an as-build floor plan) may be generated. It should be appreciated that this may be used in the planning of construction or remodeling of a building for example. Issues sometimes arise during the scanning process that results in errors in a map. These errors may be due to a mis-registration of newly acquired data with an earlier data set. These mis-registrations may occur for example when a natural feature in the environment used by the system for registration is moved. Other errors may occur due to ambiguities in the data set.
For example, in the map 20 of FIG. 1, a scan is performed that generates a two-dimensional map of a hallway 22. As the operator opens the door 24 to proceed into the room 26, the system uses the edge of the door as a reference point for registration of the data. As a result, when the room 26 is scanned and the data is combined with that from hallway 22, the room 26 will be rotated on the map relative to the hallway 22, resulting in an improperly oriented room 28.
Accordingly, while existing two-dimensional mapping systems are suitable for their intended purposes, what is needed is a mapping system having certain features of embodiments of the present invention.